Radio demonstration apparatus



July 18, 1933.- P. E. KLOPSTEG 8,

RADIO DEMONSTRATION APPARATUS I Original Filed Nov. 4, 1929 4 Sheets-Sheet 49 41 55 q 53 31 46 49 r--| -1 l 47 40 7 July 18, 1933. P. E. KLOPSTEG 1,918,402

RADIO DEMONSTRATION APPARATUS Original Filed Nov. .1929 4 Sheets-Sheet 2 July 18, 1933. P. E. KLOPSTEG 1,918,402

RADIO DEMONSTRATION APPARATUS Original Filed Nov. 4. 1929- 4 Sheets-Sheet 3 July 18, 1933. r P. E. KLOPSTEYGV' 1,

RADIO DEMONSTRATION APPARA'ILIUISYY ori inal Filed Nov. 4, 192a 4 Sheets-Sheet 2o 1 shown under varying conditions of reception p Other BlGIIlBHtS OI'; dev ces are prov ded'for 25 the accompanying drawings, in which if g, l-isie s t o e 'r ei of prt rr u Patented'luly is, 1933" 1 A E ST-BA' 'I N Arm-Runs Continuation of application Seria1No.4Q4,631, filed 'Novembelf i, 1929. Thisian lication filed r biua yfl, I

1933; 1 Serial This application is a Continuation of my copending application Serial No. 404,631, for radio demonstration apparatus, filed Novem er l, 1929. v

This invention relates to for deny onstrating by experiment the, fundamental principles .of 'radio transmission of' energy andlias amongits objects to provide'appw ratus-of this character Whichwill meet the usual "requisites of educational apparatus,

[such for example as durability,,compactness and simplicity; which win visibly demons stratethe transmissionand reception of el'ec-f V tro-inagnetic'Waveswithin thecon fines of an ordinaryfclassroom; which is sufficiently sinipie in structure, theory'and operation that a person of ordinary scientific knowledge may:

snake the deinonstrationgandwhichfhas the:

showing clearly the capacity'to setl radiations of strength that reception mayj be convincingly without the use of delicate app aratus."

7 Further obj'ec ts and"advantages; will h'e embodiment of the; oscillator; 1 v

Fig. 2 is a b tto n plan View Fig.1 is a transverse, sectional vienptaken on the line 33 ofFigwl; I n Fig. 4is an end elevational view of aslight-I ly modified form of'the oscillator unit have :Figx5 is a longitudinal,sectional View ofthe form shown in FigL 4, takenlon the lin'e- 5 5 :of-Fig; 6.

V Fig. 6 is a plan View ofth'e' modified iforin;"

' r Fig. 7 isa bottoin plan-v'iew of the same;

wiring employed" in the" oscillator circuit; :j "'f Fig. 8 isa series of'diagramniatic representations showingthe phenomena which take place in th inductive coil at diflerent stages in a cycle' o'f osc llation; I V 1 Fig. 9 is a Viewpartly nperspective partly in elevation of the; apparatus :set up; for demonstrating standing waves i i paralleljw-i 'e system lying horizontal of the mately threeInetersin length. The circuit v is diagrammaticallyshovviifin consists essentially of atransforinenhavinga pri nai-y-Q J ilQO connected to asuitable source 51 of'alternating c nrrent supply fsuch as thef iisual':11Q volt circuit, and having aghigh'i winding being connecte'd lthrouglrresistances Q8 ancl 2 9 coiidef nsers 30 @l togth-ends oif the;oscillatorlcoil23. pairot oscillator-1 ub ufoi infl ii ing th lleti 1 11 .ig. 1 0 is illustrating} typego fjref il 2:3 are1i rovided plate cefive'li'f d i edl'toishovv the "distribution io fi potential throughoutaits length;

,Fig. 11" is a sectional viewtaken ,1 Fig. 13 1 llustiate' the o curate; tint 1 5ml 1:. KLOPSTEG, or EvAnsroN, ILLINOIS, elanoma pmmitrscmnmio PANY, OF cII cAGq L InoIs, A CORPORATION OFIILLINOIS V equipped with variousgradiating antennae; I

of receiver shown-in Fig. 12;an'd r 1 ig. n is. a laviringf diagram"ofthe ,oscil f Fig. l6showsa coupler loop adapted to beuiiedlforj producing standing waves on a tions [are maintained. by ,nieans] of electron tubes, two sets of sending antennae, a" power The consists gessentiallygof a l, short wave oscillatonin which the oscillamaking various experiments; w are exampleas several small 'neo n glow lamps, afjw ve therino-galvanometer;

inYth-e neighborhood of 100,900,000 cyclespeia second,1;vvliich produces waves of approx' tag 'l' e o aryf r vin fig when; i p-i plies the {plate current for, the; oscillator 7} tubes, and a low voltage jsecondary'winding 22 supplying the filamentcurrent;

' oscillator coil ,or loop '23 has1ilts mid.- 'f

poiont Qat connectedthrough a "suitable; choke obito'oneterminal-QGofthe second;

ary Winding 21Q' the' other terrninal, 27 of the meter, an incandescent lamp, and eanjainmeter I? z I 'WlllCh, 1n th1s case,' s n the form iofiaweston I i of the transformer,

.34 and being connected to the ends of the c'oil, the grids 86. and 87 being connected through: condensers 30 and 31.,:respe ctively,

-to the opposite ends-of the coil to which the respective plates are connected. The" filam ents 38 and 39 "of theoscillator tubes receive i their energy from the low voltage winding 22 fvVhen'theoscillator is runcuenifig; a "quantity of electricity is surgingb'ack and forth at high frequency in theoscillatorlo0p The rate atwhich, thissurging takes place. s de-- termined' by the inductanceof the loop and v the distributed capacitance of the conducting c materials to which the ends of the vloop are connected The oscillation of the charge in the loop constitutes a current of high frequency associatedwith which there is acorresponding oscillating magnetlc field" wllloll xtends throughsthe loop at-Yright'angles'to P the electric field. At theinstant the current I reverses,-the ends of the loop are at a'large.

4 static field is zero;

instant the current'is maximum theelectro- ,venience will be; considered the' beginning of V 40* en'ce existsfhetween'theendsofthejloop;j At' sidejjof the loop is positive, the leftyne'gative.

potential difference and the current is zero.

This condition gives rise to 'an electrostatic field acrossthe ends of the loop: Atithe the cyclej 'x I At 'this' instant, no current is flowing through theloop buta high potential differthi's point, we" assume'that the right hand -Because ofi the electrostatic field existing- 'acrosszthefcapiacitan'cea current is set up in the loop in acounterclockwise direction, as shown'in' the second diagram. At the moment the current reaches. its maximum value, I 'the potential difl'erence between the ends of l .the loop reaches zero and the electromagnetic ing negative ch shown in thethlrd diagram.

field at right angles totlie loop reaches its maxinu'imi' Because offthe inductance in the circuit, the current continues to flow in the same direct on whlch results in an increasing positive chargeat the left and'a correspond- I arge on ;the;right side, as

When, ;;the current ,fiowingf hrough the f'loop reaches Zero, theel'ectrostatic field across f thejc'apacitan'ce is again at its Inakimunnbut withjthe positive and negative charges reversed. As aresultga clockwise; current is sent through the loopdn a manner similar to ,"that explained in connection withthesecondf i, diagram; Finally the cycleiof ioperation is completed andtheconditionsexisting atthe beginn ng offthe oycle'are once more obtained.

In the preferred embodiment of this in-' vention, the oscillator unit comprises a base 40 preferably of insulating material such as bakelite having an upstanding condenser" housing 41integral therewith Downward 1y extendingflanges 42 are provided for the base to allow a clearance for the wiring of the oscillator and various other connections."

The side walls 43 and 44 ;or the'condenser housing have secured to them suitable tube sockets 45 and 4 6; 'The securing boltst'on j the sockets extend through the side walls of the housingand serve'to hold brackets 47 in plac'e, which not only support the condensers 30 and 31, but also actjas terminals for the oscillator tubes. 'For "convenience, a

the filamentfterminals' are marke'd' in the drawings with an F. and F+, the grid terminal with theplate terminal with a comprise an insulating base 48 having f two sets of plates 49, the plates in each set being separated bynie'tal washers 50 and hel d in place "by screws 51'; Inasmuch" astut v terminals support' 'the insulating base 48,.this' provides a very sil nple construction and a great saving of material in housing thecon- -densers. v

"Theends of the inductive loopor coil 23 are connected by means of the socket bolts to the plate'ter ninalsof thesockets, The

chokecoil 25 is mounted vertically upon'the' base and is'connected by means' 'ot'a con-. 7 ductor, which may be in theform'of a coiled wire 52, to the mid-point 24 of the oscillator coil; 4' i The res stances Inasmuch as the plugs are unequally spaced from each other; the triple connector socket (not shown) l'lheconden'sers ares-0f the formfshow'n and ,which fits over them ton ake n 28 and 29'are m'ountedona vcore 53 secured to the base 40, and spring} plugs 54,55 and 56 are located, nearby to re ceive the POWGI'SLIPPlyfIOHl the transformer.

the proper connection with the-transformer cannot be'inadvertently turned end for end} when connection with the transformer is be? ing made. a

' Antennte'socketsl 57 are provided along one edge of ,thebase for receiving suitable antennae which are adapted tocooperate l with'the inductive loop in'emitting radia-f tions from the oscillator unit. ;The antenna? sockets are tapered". at. each, end as clearly shown in Fig. 1 to: more firmly engage the correspondingly" tapered ends1ofthe1fanten n8 .The location of the antennae sockets is suchastopermitverticalantennae being emj v ployed which extend below the plane of the base, in "which 'caseQthe oscillatorv ,unit is placed near the'jedge of the table or" other means of support, with the antennae sockets overhanging the table.

The wiring of theoscillator unit follows the circuit diagram otFi'g, l4, the plug 54 connecting with one'terminal r the second- L lator coil 23.

ary ,Windingx22 of gthetransformer; the plug connectingwith theterminal 26'oftheiseo ondary winding 21; and the plug 56 connecting withthe terminal 2710f thesecondary' coils; A conductor 58 serves to connectthe plug. 54f with. the: positive sides of V the fila ments, the-conductors 59-and 60 connecting. with the negative sides. of the filaments to.

complete the filament circuit.

Electrical connection is made between the ends of the resistances 28and 29'and the: grids 36 and 37 ofthe oscillator;,.tubesb m ans of the conductors 61 and 62. ,The rackets V 47 which serve as the terminals for the tube grids are electrically connected through the condensers to the ends of the oscillator-coil '23. c A short conductor 63 extends between the plug 55 and the choke .coil25 cuit. a

to complete the V cir- In the modified term" of 0551mm, the

66 i and 67 are provided for protection of the condensers. In all other respects,jthe modiez fied form is similarto theipreferred formand no further description need be given.

In both the preferred and modified forms of the oscillator unit, meansare'provided for employing horizontal antennae, as well as? xverticalflantennzef These means may take the form of tapered spring sockets 68 secured to the top of the condenser housing andtdi- 1,

.the ends' oftheoscil- I l L is being withdrawn iromfit by the'tuned system.-made up of the; wires 74,-;75 and7 6.

rectly connect'edhw ith Various forfns of antennae ma beheme 'ployed in connection with the oscillator unit,-

but preferably the antennae are in the form of hollow brass rods '69ha'vingtaperedends that may be readilyinserted in thesockets: 68. .There is also shown in-Figsifl9 and 13K a second antenna, such a's' 70, that is coupled: by means of its position withres pelct to the f coil 23 so that when current is flowinglin the. coil 23, a current iSQinduced in the loop 71 of the antenna. Vertical "extensions, such as.72-, Inay 'be provided which can hefat-f tached or detached in a manner similar to, v c

'lampand-to the body of the. experimenterqi The nodal points otpotentialcanbe' 'ye'n, more accurately, located by sliding another", 3 bridge Simi ar t h fi 1 1 61 along t e pa X allel wires. As each nodalfpdintds' passed,,

he s e emr 73 in th c ll t r wi l u denly diminish in intensity due tothe: energy that of. attaching the rods 69 to the coil 23. The operation of the oscillator hasfa'lready been described. In order to test whether or not the. oscillations farebeing produced, it:'

is only necessary to touch the exposedinetal terminals of the coil 23 with fa; piece ofmetalj or the tip of; aflead'pe'ncil. .lIfthe circuit I is operating, sparks-willibeobtainediat the the test lampglowsbrightly.

be simplyplaced across: the ends of the loop ;v

Ineither case,-,if the circuit 'is zoper'ating,

, Referring now to Fig.- 9, theremeans which insulate the. wires other. I

edasimplemethodof measuring wavelength by what-is commonlyknown as the Lecher 1 l .7 wireumethodl; Standing. waves areygenerat- 'ed on apairfof parallel wires74 -and; 7 5 by coupling the oscillator to the verticalantenria "coupler to which-thewires v74 and75iare connected- 1.Preferably, the5wireslare'great elf-than five meters in :length, and arefsupported at theirgouter-"ends-by :an fy suitable m-lee iWhen; the oscillator? is e-operating, Y indwaves are produced, Ionthe; wires :if the,

parallelpwire-systcm-is in resonance," i. e. if

' theilength of the wires bears a. definite relag tion; to the wave length. The; ends, of the wires, will,"of course,- bepoints of maxlmum potentialivariationias long astheyfare in sulated from. each other, 1, :1 7

. If, however, these w res areconnected as as i means'ofawirebridge 76,-.they willtheni f 1 beat thefsamepotentialat this point, and 1 will gfOllIl. potential nodes. The} wire bridge 7 Githen islmoved alonglthe parallel wirestof ward the oscillator until a-glow lfiLIIlP COlI- nected across the wires, as;at 7',:about,80 cm! from the antenna Z0; glows most, brightly.

This indicates then that the lcngthfof the. wires 74 and 7 5;f-rom the wirebridge 7 6 to.

their inner ends I isl a f multiple half-wave length. Whensuch; a pointiis reached, the! glow lamp connected, tofthe osci-llator coili" willyshow a] sud denjlowering in intensity due I. 3 to the fact thata greateramount otv-energy ,'The field intensity maybe also tested'lor .lVhejn the lampglowsbrightly under'th'ese ment is passing from the wirethrough the is maximum. at resonan ce.

along the wires maybe quicklyfound-, 1

.. a E Ifldesired, a: wave mQtS ItSZ' Y- 1s us ra conditions,the, current which heats its fila 1 i g -a t i C mthe .oscillator whichj; q

iilQyQdt QquiQk y'a ce ain it e e gth.o the 1. f i I V in "ta l up by the oscillator; Thisj may be accomplished in the well known manner of holding-the loop 83 of thisineter'parallelto 'catedj on thedial ofthevvave meter. Y

or: some experiments, it'may bedesirab'le to'havethe Wires 74 and 75'lie in a horizontalpl ane. This can be'easily accomplished by einploying aninductiveloop in the form of an invertedU as shown in-Fig. 16, the: tapered ends of the loop being engagea'blein the WQ socketsiprovidedin {the oscillator base.

, 1- "The foregoing description of experiments .Which are possible with the apparatus'of this invention" has dealt fWith the creation rof standing Waves on'a systemi'o'f paralleltvircs v- -;The apparatus alsofladapted andis' capa- V ble of radiating electromagneticWaves Wh1cli may be detected. Within given d'i'sta'nces by suitable receiving'cl'evices, the simplest of 'these being illustrated-inFigs. '12 and 15.

Itcomprises a pair of tubular rods 8i and which are socketed: in a} common sleeve 86 and which are provided with telescoping extensions-87 for varying the'total length of the receiving antenna. Preferably the sleeve 7 8 6 is of insulating material and is provided i Y Withmetallic' bushings-88 and 89 separated from each other atthe center ofthe sleeve.

Short metallic strips 90 and 91 are secured ;t0 the outer'iac'e of the sleeve and are electrically; connected by means-of screws 92 to their respective bushings. "An incandescent lamp socket 93 is mounted on the strip 90? V and the screvvf9 i,finsulatedfrom the lamp socket extends'through the sleeve and furnishes electrical connection Withthe strip 91;

An incandescent bulb '95 is placed in the socket-- and the base terminal' is adapted to engagetlie headof the screw 94. The-cir-g cuit, therefore, can be traced "from the tubu lar .rod 85 throughthe bushing 89, screw 92,-

strip 9'1 larnp socket screiv9t, base terminal" I v o having a telescoping rod 1 06for varylng the total length of the'receiver-s -As' shown, the electrical connections forthis'lampfwhich of thef'incandes'cent lamp, socket casing 93, f v strip 90, the' oth'er screw/192', bushing 88 and ithe tubular rod 863:.

By adjusting the length of the receiving;

unit by manipulation of theextensions 87;

fine adjustnients'may be-macleto-the setting at which the bulbfiowstmost brightly, andthis infefi'ect is another check on the wave length; i theireceivfer is turned at right angles to the sending antenna; that is to aver} tical position While theradiating ma es) are pler 7 0 and eXtensionrods'72,"it,vvill be found f Another form ot rec' e'iving shown in FigsclOa'nd 11. 'In thisreceiver the'dis V tribution of potential may bevisiblydemonstratedby the'use of a plurality of incandescent lamps placed, at I various positions along'itslength, In this constructionyvtwo that thereceivingfantenna must be placed in f a -ve1-t 1cal.tpos1tion'etoobtain the maximum elongated -W0Od8111, members 96 and 97are employed preferably square in cross section,- and theantenna 1s made up of a seriesof netallic iristrips 98 suitably carryingincan descentcbulbs '99 at. their zjfunctures. The

: particular construction employed is shown most. Clear} y in Figfill and;'as tlleleillllstratedy the member96. 'is1*provided"iyvithasleeve p engageable. with the slightly rediiced endof V the member-9'Z'fand'furnishingsuitable e'lecJ; trical: connection betweenthe t'Wo'me'mb'ersQ f More specifically, tone side ofth e filament in theiiicandescent lamp'iat theil'eft-is electrical i ly'connected through the socketlOO to the minal Witha screWlQQ insulated from the I conductorjwith a h1etallic1sleeve-103. w

:This [electrical connection is continued 1 metallic Strip l01,- -andthe" other side of the I a filament makes contactlthrough the base terthrough thezmetallicstrip 104 to :the socket, V "casingl oft-the next lamp .Where. it' is carried through the filamentland out through" thebase terminal to thenextlamp and-,so on'bj-" At the extreme right of Fig; 1-1,1-the"endlampissho -n connectedbetween one of'the' antennae strips '98 andatubular extensiona105' are 'illnstrative of the connections for the otherflamps,areinadebyconnectingthebase t im l' through'ithe screw,-107 to 'theflat I tened fend of the tubular eittension- 105;. and byallovving thelamp socket' to contact with i the raised;.end:zof:the antenna strip which leadsfrom the adjacent lamp :Q'Suitabl'e insu lating'washersaratof course; provided In place of using an electric incandescent; bulb for detecting; the presenceof 1 rad-id I Waves, a othermo-galvanometer "may teem-f pl'o yed toquan'titatively indicate 'the fielct-i strength ofthe, radiations; such' forexample as the thermo galvanometer 81 'provid'ed with "suit-able extensions With this ttype of re the radio ceiving device, the polarization 0 wave maybe strikinglydemonstrated; v Y

In each ofthe eXpenments in which the coupler 7.0 is employedythei effect of changing the. coupling byirotating" the coupler in its socket can be readily shown. For example;

by holding the receiving antenna at arms length parallel to the sending antenna made up ofthe"coupler.'70 andethee'xtensions 72,.

the change in power transferred to the receiv- 111g unit. when the coupler'is lmoved out of its parallel relation with the inductive loop 23, is shown by the reduced brillianey ofthe incandescent lamp'of the receiving unit. 7

In fact,when"the couplerdoop is at right angles to theinductive loop, thereis little,

it any, response from the receiving unit;

lhis reductlonin power transn'nssmncan,

of eourse,-be quantitatively shown by using.

the therino-galvanoineter receivingunit 81 when provided with suitable extensions.

Many other experiments may be carried outwith this apparatus .by combining different accessories therewith in various'relations,

and one in particular is worthy oi notice,

this being the polarization in two planes otthewaves so as to obtain a single polarized wave of great intensity. To accomplish this, the horizontal and vertical radiating antennae are both used as shown in Fig, 13.

1. In educational apparatus The receiver then responds in either a vertical or horizontal position, that is, whenever the receiving antenna is parallel to'one of the radiating antenna. It responds with great intensity when the receiver is tilted inone direction to an angle of 45. to the horizontal,

but when tilted in the opposite direction, to alike angle, there is no response. The reason for this is that in one pair of quadrants, the

oscillations from thetwoantennae are in phase and strengthen each other, and in the other, they are out of phase and counteract each other.

It is apparent that the invention may be embodied in other specific forms Without departing from the spirit or attributes thereof, and the present embodiments of the in- :vention are tobe considered in all respects illustrative and not IBStIlCtlVG, reference being had to the appended claims rather than to the foregoing description to indicate the scope ofthe invention.

What- I claim, therefore, is: i

for demonstrating the principlesgoverning the production of short wave oscillations and their.

transmission through space, the combination of a raised base having an integral upstanding housing thereon, a pair of condensers mounted withint-he housing, tube sockets mounted on opposite side walls of the housing, a single turn oscillator coil mounted on the top wall of the housing, antenna holders directly associated with the ends of the oscillator-- coil adapted to support a horizontal antenna, means ivlthin the housing for .elec-" trically-connectlng the condensers w1th the tube sockets to form a part of an oscillator circuit,andi asocket in the base adapted to support al 'second antenna inductlvely cou pied withthe osc llator coll. A

o 2; In educational apparatus tor 'demon-= strating "thepi'ineiples governing the pro- '15 5 transmission through space, the combination duction ofl shortj wave oscillations and their of a raised base having an upstanding'inte gral 'llOLlSlllg, two opposite slde walls 0f which are inclined 10111tl16 vertical, a tube socket mounted on eachof the incllned walls, a pair of condensers within the housing d1- rec'tly connected'to' the'tube sockets, an-os-,. cillator coil on the top vwall ofthediousin'g,

the ends of [which are electrically connected with the"tube sockets, meansincluding the condensers, tube sockets "and oscillator coil forsettingfup shortwave oscillations in the in inductive relation to' the oscillator coil,

and meansfor varying said inductive ref-L lation. i r V 3 3. A tunable receiving antenna for demonstrating to students the reception' of radio waves comprising two parts,"0ne of which includes an elongatedrod provided with extensible meansior' varying the total length of the rod, and an incandescentbulb electrically interposed between the two parts for indicating a reception er radio waves.

sulating sleeve adjacent the bulb.

\ 5. Atunable receiving antenna for demon strating to students the reception ofra'dio waves comprising two parts, one of which includes an elongated rod provided with ex:

tenna for indicating a reception of radio COll,1I1Cl' a pai'ro'f socketsfdirefctly associated with" the ends of the :oscillator co'iladapted to receive horizontal radiating antennae, means on the base for supporting an antenna tensiblel'means for varying the'total length is of therod, and an ammeterelectricallyinterposed between the two parts .for' quantita-- tively indicating a reception of radio waves, 6. A multi-part extensible receiving an waves and the distribution of potential therein and including a plurality of incandescent. bulbsfelectrically interposed between the parts of the antenna.

17. An educationalapparatus for demonstrating the principles"governingthe production of short wave oscillations andtheir transmission through space, the combination i of a base, an upstanding oscillator coil j transmission through space, the combination I I connected with and adjacent the ends of the 7 provided with extensible means for varying of a base, a single turn upstanding oscillator coil mounted on the base, means for setting up oscillations in said 0011, anten'nw sockets coil for detachably supporting oppositely extending horizontal radiating-antennae, anda vertical antenna adapted to be cletachablysupported on the base and including a single i turn loop forvariably. coupling the vertical antenna with the oscillator coi g Y 7 9. A tunable receiving antenna for demon strating to students-the reception of radio waves, comprising a two part elongated rod the total length of the rod, and means interc Q coi posed betweenthe' twt'iv parts ofthe rod for indicating a reeeptionof radio waves, said rod and means being adapted to be grasped in Q thehand and carried from place tolplace.

10. 'In' educational apparatus for demon-j strating the-principles governing the production of shortwave oscillations and their transmission through space, the combination of a base, an oscillator coil mounted on the base, means "for settlng up oscillatlons' in said coil, radiating antennae associated'with the coi1, and receivingmeansfor detecting the presence of radiated energy at'relativ'ely short distances T from the oscillator, said means comprising atwopart antenna, one

withv extensiblemeans for varying the total length of the rod, and means interposed between thectwo parts of the antenna for in-- -dics'tting a reception of radio waves, said rod and means being adapted to be graspedin the hand and carried from place to place.

' I PAUL E. KLOPSTiEG of which includes an elongated rod provided 

